Rijndael (AES) vs Twofish (AES finalist)
TrueCrypt benchmarks
Hardware-accelerated AES turned off
CPU idling at 1-5%; 6.5GB used by (idle) programs + Windows
W7 Ultimate; FX-4100 CPU
16GB 1866 RAM (2x4GB Patriot Viper 3 + 2x4GB Corsair Vengence); 9-10-9-27 timing

50MB buffer, mean encrypt/decrypt speed (MB/s)
Rijndael	Twofish
259		276
261		291
289		245
233		297
305		298
344		256
310		279
357		300
354		269
354		297
_______________________
306.6		280.8

100MB buffer, mean encrypt/decrypt speed (MB/s)
Rijndael	Twofish
308		241
320		235
284		236
323		247
303		231
298		266
314		237
309		266
323		246
315		245
_______________________
309.7		245.0

Note: though I did not record it, Serpent (2nd place AES finalist designed with twice the intended level of security) had slightly above half the mean speed of Rijndael for most runs.